Polytopic carriers for platinum ions: from digalloyl depside to tannic acid

A novel dinuclear platinum(II) complex, [Pt2m-GG(Me2SO-S)4] (8, GG = deprotonated methyl digallate), was easily synthesized under solvent-free conditions by grinding solid m/p digalloyl depside with the Pt precursor [PtCO3(Me2SO-S)2]. Similarly, platinum nuclei have been introduced into the galloyl chains of tannic acid (TA). In particular, three complexes A, B and C were prepared by reaction of TA as polytopic ligand with increasing amounts of [PtCO3(Me2SO-S)2]. The antiproliferative activity of complexes 8, A, B and C along with the corresponding ligands GG and TA was tested in vitro, in comparison with cisplatin, on two human tumor cell lines: A2780 (ovarian cisplatin-sensitive), A2780cis (ovarian cisplatin-resistant) and one non-tumoral cell line HaCat. Experiments focusing on pro-apoptotic activity indicated that the antiproliferative activity of the most active Pt(II) complexes is associated with induction of apoptosis.